<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    .top {
      margin: 0 auto;
      width: 1000px;
      /*父级标签高度为0，子级标签浮动，会影响到布局*/
      /*height: 300px;*/
      background-color: pink;
    }
    .left{
      float: left;
      width: 200px;
      height: 300px;
      background-color: green;
    }
    .right{
      float: right;
      width: 790px;
      height: 300px;
      background-color: red;
    }

    .bottom {
      width: 100%;
      height: 100px;
      background-color: black;
    }
  </style>
</head>
<body>
<!--父子级标签，父级没有高度，子级浮动，后面的标准流会受到影响-->
<div class="top">
  <div class="left"></div>
  <div class="right"></div>
  <!--    解决浮动标签影响方法1：加一个块级标签 clear: both  缺点：网页结构变乱-->
  <div style="clear: both"></div>
</div>
<div class="bottom"></div>
</body>
</html>